Under the conditions created by the conveyorization necessary in present-day warehousing, manufacturing and article transport, it frequently becomes necessary at times to relieve the load on one article transport line by diverting a portion of the load to another conveyor line. In the past, this has been done largely by labor or, in other cases, by installing two separate lines with the load factor on each being totally independent of the other. This often causes under usage of both systems, resulting in unnecessary costs for both labor and capital equipment. It is not a satisfactory solution to simply close one of the lines during low demand periods. This does not solve the problem when one line is overloaded and the other under used. The invention also makes it possible to concentrate the load entirely on one of the two conveyors when demand is small enough to justify it. It is the purpose of this invention to provide a single solution to each of these problems.